A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

learn more… | top users | synonyms (1)

0
votes
0answers
5 views

Poisson Regression vs. T-test for Balance

I have many subjects that were cluster-randomized to a treatment group and to a control group. I want to check the age balance of the groups following the randomization - e.g. whether there is a ...
0
votes
1answer
21 views

Why does a p-value of 2.4 indicate a very small probability that rejecting H0 is incorrect?

I am working with body temperatures in R, conducting a t-test. It is widely believed that the average body temperature for healthy adults is 98.6 degrees Fahrenheit. The body temperatures of $n = ...
2
votes
1answer
29 views

Why would one ever use z-score over a t-score?

Forgive me if this seems like an elementary question, but no amount of googling has turned up a satisfying answer for me. From what I understand, a t-score should be used instead of a z-score when the ...
1
vote
0answers
11 views

What's the difference between t-test and sequential F-test?

I just started learning linear regression, and I couldn't completely understand the difference. I know the t-test is testing NH:$\beta_i = 0$ and AH: $\beta_i \neq 0$. The overall F-test is testing ...
0
votes
2answers
32 views

Can you derive Standard Deviations from a raw mean difference and p-value?

I have mean averages and a p-value, which I assume was of a t -test. This is the information provided to me: Treatment N =121 Control N=107 treatment mean = 356.700 treatment control= 357.560 ...
1
vote
1answer
31 views

Can I interpret mean difference on a Likert scale as a percentage change

I have pre-test data showing a mean of 3.71 for work-stress (7 point likert scale). My post-test data shows a mean of 3.24 for work-stress (same 7 point likert scale). Paired sample t-test is ...
1
vote
1answer
28 views

Paired t-test with small standard error

I am comparing two algorithms applied to all frames of a video clip. To evaluate the result I am doing a paired t-test analysis, i.e., I am subtracting the algorithm scores for each frame and then ...
2
votes
0answers
13 views

Identify differentially expressed genes across genotypes

I have 40 different genotypes of rice. For each genotype, I have two replicates under control treatment and two replicates under drought treatment. We sequenced those samples and get read counts of ...
2
votes
1answer
31 views

How do I avoid multiple t-tests (or is it ok to use multiple t tests here?)

I've searched around CV for a bit, and have not found a good answer as to what test to use instead of multiple t-tests in my particular situation. I am interested in comparing mean size (of fish) ...
0
votes
1answer
28 views

How to test multiple comparisons of means of variables in R

I have a multiple N (>20) variables. I want to test $H_0$ that in at least one pair of them one variable have significantly higher values then the other. I know that I can perform a bunch of $\frac{...
1
vote
0answers
14 views

statistical test to compare numerical data pre and post intervention

For my research I will be comparing the mean number of screening tests performed before implementation of an intervention and after. The pre and post groups are not the exact same participants. The ...
4
votes
1answer
106 views
+50

Real-world example on significance testing with large samples

The issues that arise when one uses statistical hypothesis testing framework with large samples are dissussed on CV (see e.g. this thread). The main problem discussed there is that in the real world ...
0
votes
0answers
6 views

How do I find if two categories of ratio data are different in a manner that is statistically significant?

I have 4 categories of data, A, B, C, and D, that are ratios (market share). Each category has different numbers of records (prescriber-level data). Each record is a market share percentage that is ...
1
vote
1answer
28 views

one sample t-tests applied to each row - 'data are essentially constant' error

I have three replicates of an experiment which gives me ratios of the abundance of different peptides. If I take the data for one peptide: ...
1
vote
0answers
26 views

What is it that you're doing when you do a single t test on one predictor of a multiple regression model?

I hope my interpretation is correct. When you're doing a t-test on a single predictor of a multiple regression model, are you looking at how it behaves while the other coefficients are fixed?
0
votes
0answers
13 views

Paired T-test vs. Survey Design T-Test with Stratification

What is the difference between survey design based approaches to t-tests when there is a stratified sample and paired t-tests where the pairs are the strata? For example, in R there is a svyttest() ...
3
votes
0answers
74 views

Single Sample t-test Hypothesis Confusion

In case you want data set.seed(100) hotel <- rep(1,100) hotel <- unlist(lapply(hotel, function(x) { runif(1,1,5) } )) NULL Hypothesis :- Hotel rating is ...
1
vote
1answer
30 views

Performing a t-test with discrete (currency) data

I want to perform a 2 sample t-test assuming unequal variances, however my variable is currency. Currency is discrete, however when checking the assumptions of the t-test, I see that the data should ...
0
votes
1answer
34 views

How to find the p-value of a t-test using the critical value?

I keep looking over the lecture and they just seem to skip how they get from the critical value to the p-value, but we need to be able to do this for the exam! So I've calculated the test statistic $(...
3
votes
1answer
19 views

Only interested in select pairwise comparisons - Do I need to run an ANOVA first?

I have data with two biological factors. The first factor has 2 levels (say, Alive vs. Dead) and the second factor has 80 levels (protein of interest). I'm only interested in whether the mean value ...
2
votes
0answers
24 views

probability of a single value belonging to a population

what is the appropriate approach to estimate the probability of a single sample belonging to a population? Specifically, I am calculating a particular value from the comparison of two time series. ...
1
vote
0answers
13 views

Pre and Post intervention with no pairing

My sample size is small (n= 28). I have 2 cohorts who have carried out the same interventions at different times. I have collected pre and post intervention scales for both groups. What I have not ...
0
votes
2answers
37 views

Which test should I use to compare the means of two factors (motivations), which were surveyed at one time, of one sample?

I conducted the Academic Motivation Scale. This instrument returned three types of motivations, namely extrinsic, intrinsic and amotivation. The latter motivations means the absence of motivation ...
0
votes
0answers
20 views

How to generate t-test with data sets on different scales?

Let's say you repeat an experiment on two different days. On day 1 you get the following data: Day 1 ...
0
votes
0answers
8 views

Statistical test to determine most accurate method

This is probably a basic question, so apologies. I am trying to determine what is the most accurate reconstruction method out of 11 options, for which I have results for 15 specimens. I've looked into ...
1
vote
1answer
13 views

Paired t-test for repeated measurements, but with 2 missing samples.

I am doing a gene expression analysis on blood samples collected from the same 8 goats. My sampling points are before LPS-treatment (0h), and 1h, 2h, 5h and 24h after treatment. I want to compare the ...
1
vote
1answer
43 views

For model selection/comparison, what kind of test should I use?

I trained and tested two models on the same dataset in a 10-fold cross validation manner. I want to show that one model is supreme than the other. Therefore, I want to show the better model has a ...
0
votes
0answers
48 views

Estimation of the probability of the winner's curse

The increase in false-positive results arises primarily from an overestimation of effect sizes, leading to upward-biased effect sizes that often cannot be reproduced in follow-up studies (‘the winner'...
1
vote
1answer
41 views

Which test to calculate the p-value?

so I have a data set of 1500 proteins. I then identify a set of 50 proteins and lets say 40 of these 50 have a certain function. I then draw 1000 random samples of size 50 from my initial 1500 protein ...
0
votes
1answer
25 views

Estimating dependent t-test for paired samples when only means and SDs are available

I'm attempting to extract t-values from a series of published papers for a meta-analysis. The specific measure of interest is the difference in performance (proportion correct on a memory test) ...
0
votes
2answers
27 views

Calculating the t statistic

I recently came across a blog post (https://cssanalytics.wordpress.com/2014/02/12/probabilistic-momentum-spreadsheet/) that discusses calculating a t-stat as part of their model. However, the formula ...
0
votes
1answer
29 views

How to calculate percental change of two time series?

I have the two sets of data; $A = $ 1.5010, 1.3118, 1.4219, 1.1650, 1.2720, 1.5421, 1.4211, 1.1832, 1.5378 1.4357, 1.2707, 1.2411, 1.4833, 1.5578 and $B = $ 1.4039, 1.1912, 1.3596, 1.4168, 1....
0
votes
1answer
46 views

How to do hypothesis testing for many individual means over time?

There is a data set that has yearly data for mean values of the number of ice creams eaten for 5 persons. The data set has values for 5 persons and 5 years(5x5 panel). Suppose due to some theory it is ...
0
votes
0answers
14 views

Pairwise comparison of stats with repeated measures

I have a data set of participants with four sets of test results, two pre- intervention and two post. So far I've been averaging the two test scores and using a paired t-test to compare the results, ...
0
votes
0answers
7 views

Formula to convert test-retest reliability into SD of difference

Wanting to work out the statistical power of a repeated-measures t.test. This requires an estimate of the SD of differences within pairs (the correlation between measures for a given person is what ...
1
vote
2answers
34 views

Significance level in sample size calculation and in final analysis

Imagine that for the purpose of a study a sample size is computed with the following formula for a given power $1-\beta$, difference in means $\epsilon$, standard deviation $\sigma$ and significance ...
0
votes
0answers
20 views

T-test or repeated measure ANOVA?

I am a Phd student in neuroscience and not so knowledgeable in statistics. I have done an experiment and am not sure if i should use repeated measures ANOVA or independent T-test. The experiment is ...
0
votes
0answers
20 views

Degrees of freedom of t-test in multiple regression [duplicate]

In regression, $ t=\frac{\hat{\beta}-\beta}{se (\hat{\beta})} $ and the degrees of freedom of t-test is (n-k) because we estimate $\hat{\sigma}^2$ from RSS and the RSS has (n-k) degrees of freedom (...
0
votes
0answers
9 views

type 1 and type 2 errors for non-normal residuals in a regression

I did a regression and performed a normality tests on my residuals, which reject the Null Hypothesis that the residuals are normally distributed (the true distribution seems to be flatter with fatter ...
1
vote
1answer
29 views

Advantage/acceptability of using contrast codes to conduct pair-wise comparison vs. t-test on subset of data?

I conducted a study with three conditions (A, B, and C) and I want to test the difference between A and C. My default approach would be to run a t-test (or its equivalent) on a subset of the data (...
2
votes
1answer
76 views

t-Test residual analysis

I'm reading Experimental Design and Analysis by H.Seltman (http://www.stat.cmu.edu/~hseltman/309/Book/Book.pdf) and working on the provided HCI dataset (SPSS format, can be downloaded from page 143). ...
0
votes
0answers
14 views

Mann-Whitney output confusion

In an experiment I exposed each of 4 subject groups to a different condition to observe the impact on dependent variable. Assumptions for parametric tests were violated hence I decided to employ non-...
0
votes
0answers
19 views

Dealing with seeming outliers in microarray gene expression data

I have the following microarray gene expression data for one gene let us say. BTW - have similar data for the same subjects across 17000 genes, so I am looking for a generalized solution. ...
1
vote
0answers
43 views

Is there a statistically significant difference between two methods, which test should I use & am I violating random assumption?

I collected data for every 2016 Republican primary that has available at least 3 polls, according to the polling data aggregated by RealClearPolitics.com. In a spreadsheet for each row which indicates ...
0
votes
0answers
19 views

Why can you use wald-test but not t-test in logistic regression

The books I read about logistic regression always use the wald-test or the lr-test for testing the significance of the coefficients. But they don't mention why others such as t-test cannot be applied. ...
6
votes
5answers
738 views

How can we ever know the population variance?

In hypothesis testing, a common question is what is the population variance? My question is how can we ever know the population variance? If we knew the entire distribution, we might as well know the ...
1
vote
1answer
19 views

How to evaluate level of significance of two similar correlations?

I have four datasets: A1, A2, B1, B2. Every dataset has between 100-300 items. Every item in every dataset has two values: x, y The goal: Find what datasets have similar x values. If the datasets ...
0
votes
0answers
21 views

Calculating standard deviations and testing the null hypothesis in a biological sample with n = 6

I am doing experiments on the viability of cells after treatment with different amounts of a certain substance. I have split my original cell line into 6 separate flasks at 3 days after unfreezing. ...
0
votes
1answer
18 views

How to work with repeated measures data paired t-test where sub groups seem to show opposite effect?

I have data that looks like this for repeated measures for the same subjects. Note, the flag column is something I just added to indicate whether there is an increase or decrease in pre vs. post for a ...
0
votes
1answer
22 views

one sample t test by grouping variable with more than 2 groups

I am having trouble finding any examples of one sample t test comparing the group mean to zero where the grouping is not binary, in R. For example comparing the heights by ethnicity to 5 ft (not ...